[time-nuts] Typical EFC frequency response (bandwidth) of a OCXO
Rick Karlquist
richard at karlquist.com
Sun Dec 17 04:48:34 UTC 2006
Stephan Sandenbergh wrote:
>> charts, it is my guess that the loop bandwidth will be in the order of
> 1kHz.
> Thus, if I can't modulate the 100MHz OCXO at this rate, I will have to
> think
> of another plan.
>
First of all. realize that the modulation bandwidth of the VCO has
to be at least 10 times the loop bandwidth and preferrably a lot
more in order for it not to seriously decrease the loop damping factor.
Hence, 1 kHz loop bw is completely unrealistic for a crystal oscillator.
The typical 3 dB resonator bandwidth of a crystal is only a few dozen
Hz. This alone restricts the modulation bandwidth to a 10 Hz at best.
In particular, in the 10811, the ALC loop will react adversely to
fast modulation, and turns out to the be limiting factor.
If you want to clean up a crystal oscillator, you need to use a phase
modulator following the oscillator.
Rick Karlquist N6RK
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